CVE-2020-21523

Name: CVE-2020-21523
Creator: NVD / NIST
Published: 2020-09-30T18:15:23.96+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.59%

Last modified Jun 17, 2026

CVE-2020-21523 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. A Server-Side Freemarker template injection vulnerability in halo CMS v1.1.3 In the Edit Theme File function. The ftl file can be edited. EPSS estimates a 2.59% chance of exploitation in the next 30 days.

Description

A Server-Side Freemarker template injection vulnerability in halo CMS v1.1.3 In the Edit Theme File function. The ftl file can be edited. This is the Freemarker template file. This file can cause arbitrary code execution when it is rendered in the background. exp: <#assign test="freemarker.template.utility.Execute"?new()> ${test("touch /tmp/freemarkerPwned")}

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.59%

83.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-74

Affected Software

Vendor	Product	Versions
Halo	Halo	1.1.3

References

https://github.com/halo-dev/halo/issues/419Exploit, Issue Tracking, Third Party Advisory
https://github.com/halo-dev/halo/issues/419Exploit, Issue Tracking, Third Party Advisory

Timeline

Published: Sep 30, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-21523?

How severe is CVE-2020-21523?

CVE-2020-21523 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.59% probability of exploitation in the next 30 days.

How do I fix CVE-2020-21523?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-21523?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST